1. Technical Field
The present invention relates to a semiconductor light-emitting device, a super luminescent diode, and a projector.
2. Related Art
A super luminescent diode (hereinafter also referred to as “SLD”) is a semiconductor light-emitting device that can provide an output up to about several hundreds of mW with a single device in optical output characteristics similarly to a semiconductor laser while exhibiting incoherent properties and a wideband spectrum shape similarly to an ordinary light-emitting diode.
The SLD is used as, for example, a light source of a projector. For realizing a small and high-luminance projector, it is necessary to improve the luminous efficiency of the light source, reduce loss in an optical system, and reduce the number of components. With the use of the SLD as a light source, a dichroic mirror necessary for a color separation optical system and a rotating diffuser necessary for securing the safety of a semiconductor laser and reducing speckle noise can be eliminated.
For example, JP-A-2012-43950 discloses an SLD including an optical waveguide including a straight waveguide portion and a curved waveguide portion.
In the SLD described above, however, light guided in an active layer is exponentially amplified toward a light exiting portion side (low reflectance side). Therefore, the number of carriers becomes insufficient relative to light on the light exiting portion side. Due to this, gain saturation occurs, so that light output is reduced in some cases.